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MGK Comments on the Preliminary Work Plan

MGK Comment: Page 5, Ecological Risk, with respect to pyrethrins in the environment, they 

are one of the shortest-lived active ingredients, with half lives on the order of hours rather than 

days. Further, with respect to the CBD lawsuit, we believe that ecological risk assessments on 

pyrethrins will not trigger levels of concern in the environment. 

EFED Response: EFED acknowledges pyrethrins appear to be labile to certain routes of 

degradation/ metabolism. Under anaerobic conditions, it seems to persist longer (t1/2 = 86 

days). In the last risk assessment performed on these chemicals, there were exceedances 

of acute and chronic levels of concern for both freshwater and estuarine/marine aquatic 

animals, as well as benthic organisms. The acute and chronic levels of concern (LOCs) 

were not exceeded for listed or non-listed mammals or birds. For environmental fate and 

ecological risk assessment supporting the forthcoming registration review, all the 

available environmental fate and ecological effects data will be evaluated. 

MGK Comment: Page 6. Ecological Toxicity Data Gaps, the Pyrethrins Joint Venture and 

Piperonyl Butoxide Task Force II, of which MGK is a member, has provided EPA with a special 

study design under the GLN 850.1020, to investigate the acute aquatic toxicity of combinations 

of concentrations of pyrethrins and piperonyl butoxide (PBO). Studies are underway 

determining the LD50 of Hyalella Azteca to these different combinations of concentrations. We 

will be able to determine both the critical concentrations of PBO and pyrethrins as well as what 

ratio of PBO to pyrethrins result in the greatest LD50. This will be extremely useful information 

from which data with other pyrethroids can inform any synergistic effect of PBO and pyrethroids 

in the environment. 

EFED Response: EFED acknowledges the comment and supports the data submission. 

MGK Comment: Page 11. With respect to Water Quality, pyrethrins have a very short half life 

in the environment, degrading rapidly in sunlight. Therefore we are very surprised to read of 11 

body-of-water impairments listing pyrethins. We will respond further during Registration 

Review. 

EFED Response: It was noted that the summary document says that there are several 

bodies of water impaired due to the presence of pyrethroids (not pyrethrins). However, 

pyrethroids are related synthetic chemicals with a similar backbone structure. EFED will 

be investigating whether pyrethrins were directly or indirectly implicated in these 

impairments. 

MGK Comment: Page 11. With respect to CDPRs recent proposed restrictions to 17 

pyrethroids used by pest control applicators, we would like to point out to EPA that pyrethrins is 

NOT one of the 17. 
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EFED Response: Acknowledged. The proposed DPR Regulation No. 11-004, which 

contains the full list of 17 pyrethroid active ingredients affected by the rule, is located at 

http://www.cdpr.ca.gov/docs/legbills/rulepkgs/11-004/notice.pdf. 

MGK Comment: Page 12. MGK recognizes the importance of more refined use and usage 

information to inform and refine ecological risk assessments for pyrethrins. MGK and the 

Pyrethrins Joint Venture (PJV) will do their utmost to provide more detailed information as 

outlined in the Summary document. 

EFED Response: Refined use and usage information will be valuable information that 

EFED will consider in the forthcoming ecological risk assessment, especially if 

refinements are needed. 

MGK Comment: As a member of the Residential Exposure Joint Venture (REJV), the original 

survey database, and the new one just getting underway, will provide highly refined use and 

usage information for consumer products containing pyrethrins. We urge the Agency to use the 

Surveys since they can be mined for detailed information that can refine ecological risk 

assessments for outdoor products. 

EFED Response: Information derived from these surveys will be considered in deriving 

accurate use profiles of pyrethrins in the forthcoming ecological risk assessments. 

MGK Comment: Pyrethrins when synergized with PBO, are important and useful Vector 

control product, as a mosquito adulticide. The short half-lives of pyrethrins minimize impacts on 

the environment and non-target species. Adulticiding products are in development which can be 

sprayed over organic crops to provide more comprehensive vector control for organic food. 

EFED Response: EFED acknowledges the comment. Since adulticides are more 

efficacious if they come into contact with insects in flight and less effective if applied 

directly to water, they are applied as mists that remain in the air for longer periods than 

traditional agricultural sprays. It is noted that while hydrolysis and photolysis half-lives 

are relatively short, adulticide applications of pyrethrins are likely mainly at dawn/dusk 

hours where the level of light is minimal and therefore during these times photolysis 

would be significantly slower. The modeling approach will be refined to include spray 

drift using the AGricultural DISPersal model (AGDISP v. 8.131

) rather than assuming 

default spray drift parameters (used for agricultural applications) in PRZM/ EXAMS. 

AGDISP will be used to estimate the application efficiency and downwind deposition to 

the water body as a result of adulticide application. Results of the Spray Drift Task Force 

(SDTF) field studies were used to validate the model results under agricultural 

conditions. Despite the differences between agricultural and mosquito adulticide 

 

1

 See the following site (accessed 03/12/2012) 

http://www.epa.gov/pesticides/science/efed/policy_guidance/team_authors/endangered_species_reregistration_work

group/esa_agdisp_fardrift.htm 
4 

applications, reports from researchers also suggest that AGDISP is an appropriate 

prediction tool for mosquito adulticide applications (e.g., Mickle 20052

). The output 

parameters of major interest to EFED from AGDISP are the application efficiency or the 

spray block deposition (fraction of the material that deposits in the swath under the 

aircraft) and the downwind deposition (equivalent to the spray drift, obtained from the 

toolbox “Deposition Assessment”). The application efficiency and the level of drift from 

Ultra Low Volume (ULV) applications derived from this model will be used in the 

aquatic exposure models PRZM/EXAMS. As noted in the Re-registration Eligibility 

Decision EFED chapter, both the levels of drift and application efficiency are 

substantially decreased when the boom height was higher than initially assumed. 

MGK Comment: Page 16. Ecological effects: Yes, by direct contact pyrethrins is highly 

acutely toxic to bees, but we would like to point out because of the short half-life in the 

environment pyrethrins would not have long-term toxicity to bees exposed to treated foliage over 

time. 

EFED Response: EFED Response: Per the previous comment, EFED will characterize 

the environmental fate of pyrethrins using appropriate models and field residue data. 

Regarding the potential for pyrethrins to cause adverse effects on bees as a result of 

exposure due to existing uses of the chemicals, EFED will utilize available information to 

qualitatively characterize potential risks to bees and the need for appropriate label 

language. EFED further notes that procedures for quantifying risks to honeybees and 

other insect pollinators and the data needed to inform that process will be evaluated at a 

FIFRA Scientific Advisory Panel (SAP) currently anticipated in fall, 2012. Based on the 

outcome of this SAP, the need for any additional data for evaluating risks to pollinators 

and/or appropriate label language will be determined. 

Physicians Committee for Responsible Medicine Comment on Avian Toxicity Test

PCRM Comment: The Summary Document indicates that the Agency may request testing for 

avian acute oral toxicity, however, available data already exists for six pyrethroids (Allethrin, 

Cypermethrin, Metofluthrin, Resmethrin, Tefluthrin, and Tetramethrin), with the Agency 

requesting testing for an additional 10 through the Registration Review process. While it is 

understood that the CMG designation applies to mammalian toxicity, the Agency should 

consider whether this is also the case for avian acute toxicity. Is it simply unacceptable to test 

every single member of these two groups of substances in lethal bird tests. 

EFED Response: As of July 1, 2008, the CFR 40 Part 158 pesticide data requirements 

now include avian acute oral data for one passerine species and either a waterfowl or an 

upland game species for outdoor end-use pesticides for all new federal actions (72 FR 

60957, dated October 26, 2007). Additional avian acute oral toxicity data for passerine 

species are intended to provide information to assess differential sensitivity on a 

 

2

 Mickle, R.E. 2005. Direct comparison of deposit from aerial and ground ULV applications of malathion with 

AGDISP predictions. A report to Institut national de santé publique du Québec (INSPQ) by REMpC Consulting, 

dated 02/10/2005 (REMSpC Report 2005-02). 
5 

chemical-specific basis, determine whether assumptions of allometric relationships can 

be confidently applied to chemical classes that have not been tested, and to include a 

taxonomic group of avian wildlife that is highly represented in most pesticide use areas 

and may potentially exhibit differences in metabolic rate, physiology, and toxicokinetics 

from the currently tested waterfowl and upland game test species. 

Only a small pesticide toxicity data set is available for passerine species of birds. 

Currently, no acceptable avian acute oral data with a passerine species have been 

submitted to the Agency for pyrethrins or any pyrethroid, including the six pyrethroids 

mentioned in the public comment (allethrin, cypermethrin, metofluthrin, resmethrin, 

tefluthrin and tetramethrin). Furthermore, a recent study by Addy-Orduna et al. (2011) 

indicated that some passerine species may be up to 13X more sensitive than some nonpasserine species to formulated beta-cyfluthrin3

. As additional information on the toxicity 

of this class of insecticides to passerine species becomes available, options for bridging 

toxicity data for additional passerine species could be considered. 

 

3

 Addy-Orduna, L, Zaccagnini, M, Canavelli, SB, Mineau, P. 2011. Formulated Beta-Cyfluthrin ShowsWide 

Divergence in Toxicity among Bird Species. J. Toxicol. vol. 2011, Article ID 803451, 10 pp.